Loans (Composition Of Loan Portfolio By Class Of Loan) (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020		Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		$ 7,168,745	$ 7,177,785
Financing Receivable, Allowance for Credit Loss		(86,886)	(85,675)		$ (61,503)	$ (56,679)
Loans and Leases Receivable, Net Amount		7,081,859	7,092,110
Financing Receivable, Accrued Interest, before Allowance for Credit Loss		19,700	20,653
Loans and Leases Receivable, Recorded Investment			7,198,438
Construction Real Estate Commercial [Domain]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		223,318	226,991
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			572
Loans and Leases Receivable, Recorded Investment			227,563
Construction Real Estate Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		114,110	116,430
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			235
Loans and Leases Receivable, Recorded Investment			116,665
Construction Real Estate - Installment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Recorded Investment			941
Residential Real Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		541,968	526,222
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			1,161
Loans and Leases Receivable, Recorded Investment			527,383
Residential Real Estate - Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		1,077,696	1,096,358
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			947
Loans and Leases Receivable, Recorded Investment			1,097,305
Residential Real Estate - HELOC [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		171,388	182,028
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			647
Loans and Leases Receivable, Recorded Investment			182,675
Residential Real Estate - Installment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		7,601	8,436
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			22
Loans and Leases Receivable, Recorded Investment			8,458
Commercial, Financial, and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Recorded Investment			1,595,517
Commercial Financial And Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		1,587,978	1,588,989	[1]
Financing Receivable, Allowance for Credit Loss		(16,279)	(25,608)		(21,544)	(20,203)
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			6,528
Loans and Leases Receivable, Recorded Investment	[1]		1,595,517
PPP loans receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		386,990
Bank Overdrafts
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		2,373
Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance	[1]	1,756,921	1,748,189
Financing Receivable, Allowance for Credit Loss		(24,487)	(23,480)		(11,591)	(10,229)
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			6,017
Loans and Leases Receivable, Recorded Investment			1,754,206
Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		1,665,208	1,659,704
Financing Receivable, Allowance for Credit Loss		(25,729)	(17,418)		(13,728)	(12,211)
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			4,510
Loans and Leases Receivable, Recorded Investment			1,664,214
GFSC loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		5,225
Check loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		2,109
Finance Leases Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		22,557	24,438
Financing Receivable, Allowance for Credit Loss		(541)	(518)		$ (130)	$ (115)
Financing Receivable, Accrued Interest, before Allowance for Credit Loss			14
Loans and Leases Receivable, Recorded Investment			$ 24,452
Consumer less GFSC and Check Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		1,657,874
Commercial Financial Agricultural less PPP and Overdrafts
Financing Receivable, Credit Quality Indicator [Line Items]
Loan balance		$ 1,198,615

[1] Included within each of commercial, financial and agricultural loans and commercial real estate loans is an immaterial amount of consumer loans that were not broken out by class.(2) Results for reporting periods beginning after January 1, 2021 are presented under ASC 326, while prior period amounts continue to be reported in accordance with previously applicable U.S. GAAP. Category was not broken out as a separate class at December 31, 2020.